In high volume printing of multi-page publications such as books, magazines and brochures it is common to print multiple pages on a large sheet known as a signature. The signature is printed both sides in a printing press, then folded, and cut to form a section of the publication. Most publications are made up of many sections, especially those with a large number of pages.
Making a plan for positioning the individual pages on a sheet is known as imposition. Imposition must take many factors into account to ensure that when the publication is bound the pages will be in alignment and correctly sequenced. To reduce the possibility of an imposition error in the final printed press sheet it is common to make an imposition proof prior to running the signature on press. The imposition proof should be an accurate facsimile of the press sheet signature and in particular the correct alignment of individual pages is critical to produce a useful proof sheet.
Due to the high cost of press time it is not practical to run the imposition proof on the printing press. This has lead to the proliferation of stand alone proofers that are specifically designed to make a proof sheets. In recent years there has been considerable interest in using inkjet printers for this purpose. Wide format inkjet printers represent a cost effective alternative to other more costly proofing methods that have been employed in the past. Additionally, inkjet printers equipped with higher imaging quality may also produce images of sufficient quality to serve as a color proofs. One such proofing solution is the Creo Integris™ system that combines a proof controller, an EPSON Stylus ™ Pro 7600 or 9600 or other suitable wide-format inkjet printer and specially qualified inks and media for producing imposition and color proofs.
One problem that presents in adapting commercially available printers to print imposition proofs is maintaining accurate alignment of images to the media sheet. There is a particular problem in double sided printing where it is necessary to align images on the front and back of the printed sheet to within±1 mm or better. Automated solutions such as Spinjet™ made by TechSage of Denmark automatically flip the sheet for reverse side printing while simultaneously taking care of alignment. Unfortunately such add-on hardware is often even more expensive than the printer itself. On the other hand manual flipping of the sheet is very prone to operator error and most moderately priced printers are not equipped to take account of a skewed media sheet.
With a wide proliferation of high quality and low cost wide format printers there is a need for better methods and apparatus for aligning media sheets used in the preparation of proofs. There is a particular need for an in-expensive add-on to such printers that allows accurate manual registration of media sheets.